IMPROVED RESPONSE OF UNI-TRAVELING-CARRIER PHOTODIODES BY CARRIER INJECTION

We have studied the ultrafast response of uni-traveling-carrier photod iodes with photo-absorption layer doping levels from 2.5 x 10(17) to 2 .5 x 10(18) cm(-3). It is found that 3-dB band width increases with th e output voltage in the low output region. This enhancement is more pr ominent for a lower doping level in the photo-absorption layer. From t he analysis of the carrier transport in the photo-absorption layer, we attribute the observed enhanced bandwidth as a result of the self-ind uced electric field associated with carrier injection.